By GREGORY ZELLER //

After a courtship that lasted the better part of a year – what South Nassau referred to as “a period of exclusive negotiations” – the nearly century-old Oceanside hospital will become the flagship Long Island facility for the New York City-based healthcare giant, according to an affiliation agreement jointly announced Wednesday by trustees of both institutions.

Final state regulatory approvals are expected in the coming months, according to a South Nassau statement. The plan is for the hospital’s Board of Directors to “retain local governance over the day-to-day operations,” the statement notes, with two members of the Mount Sinai Board of Directors joining the South Nassau board and two South Nassau board members becoming Mount Sinai directors.

South Nassau President and CEO Richard Murphy also retains his post, reporting directly to Mount Sinai Health System President and CEO Kenneth Davis.

South Nassau will become the eighth hospital in Mount Sinai’s $7 billion healthcare system, which already boasts some 200 practicing physicians and 11 multidisciplinary practices on Long Island.

Richard Murphy: Unique opportunity.

The 455-bed, 3,500-employee hospital will benefit from the health system’s academic, clinical and research expertise, including affiliations with the prestigious Icahn School of Medicine at Mount Sinai, the Manhattan-based institution consistently ranked among the nation’s best medical schools.

Aligning with the integrated health system (which counts 300-plus ambulatory practices, a dozen ambulatory surgical centers and more than 6,500 primary and specialty care physicians among its regional assets) means South Nassau can offer medical care on par with any other Long Island facility – “a unique, once-in-a-generation opportunity that will expand the delivery and availability of advanced, high-quality healthcare services for all Long Islanders,” according to Murphy.

“South Nassau and Mount Sinai have a shared vision to improve services, especially on the South Shore,” the hospital CEO said Wednesday. “[That’s] why this affiliation makes so much sense.”

Joseph Fennessy, the chairman of South Nassau Board of Directors who led lengthy affiliation talks that stretched over most of 2017, agreed that “our goal from the outset was to find a partner seeking to expand services on Long Island who, like us, puts patients first.”

“We have found that partner in Mount Sinai,” Fennessy added. “Their physicians and researchers are leaders in their respective fields in so many key areas of medical science.

“We know the residents of the South Shore in particular will greatly benefit from this affiliation.”

Kenneth Davis: Big win for Long Island families.

The South Nassau alliance indeed represents Mount Sinai’s “commitment to broadening access to innovative treatment and research in the region,” according to Davis.

“This transformative partnership will complement our existing network of talented clinicians and facilities,” the health system CEO said in a statement. “We are thrilled about what this means for patients and families on Long Island, and look forward to working closely with our Long Island partners to continue advancing care in the region.”

Naturally, the merger will also juice up South Nassau’s ambitious expansion plans, which actually advanced steadily throughout the lengthy negotiations. Upon regulatory approval, Mount Sinai plans to “infuse” South Nassau’s master facility plan with roughly $120 million in capital contributions, adding to what Murphy called a period of “tremendous growth and expansion at South Nassau.”

“Our plans to renovate and nearly double the size of our Emergency Department in Oceanside are already underway, as are plans for a new, four-story, high-intensity building in Oceanside, as well as expanded medical services in Long Beach,” the hospital honcho said Wednesday. “The relationship with Mount Sinai will accelerate our plans and provide essential services to patients throughout Long Island.”